Leslie Gains-Germain
Data from Alaska Department of Fish and Game
Question 1: Is there evidence that the distance Seward charter boats travel to fish for bottomfish has changed over the years 1993-2014?
Question 2: Is there evidence of a change in the mean length of halibut caught by Seward fishermen over the years 1994-2013?
| abbreviation | description |
|---|---|
| H | halibut exclusively |
| B | any combination of bottomfish (halibut, rockfish, lingcod, Pacific cod, sharks) |
| B+S | any combination of bottomfish and salmon (e.g. halibut+coho) |
The odds of fishing in Cape Cleare in \(2014\) are estimated to be \(2.43\) times the odds of fishing in Cape Cleare in \(1993\), with a \(95\%\) confidence interval from \(1.22\) to \(4.92\) times.
The odds of NOT fishing in Resurrection Bay in \(2014\) are estimated to be \(2.78\) times the odds of NOT fishing in Resurrection Bay in \(1993\), with a \(95\%\) confidence interval from \(1.32\) to \(5.82\) times.
| port | sector | date | age | length | sex | statarea | length.in | area |
|---|---|---|---|---|---|---|---|---|
| Seward | Charter | 5261994 | 11 | 120.0 | F | 495938 | 47.24 | resbay |
| Seward | Charter | 5261994 | NA | 128.0 | F | 475934 | 50.39 | capecleare |
| Seward | Charter | 5261994 | 13 | 85.0 | M | 475934 | 33.46 | capecleare |
| Seward | Charter | 5261994 | 13 | 85.5 | M | 475934 | 33.66 | capecleare |
| Seward | Charter | 5271994 | 11 | 126.5 | F | 485935 | 49.80 | junken |
| Seward | Charter | 5271994 | 11 | 95.8 | F | 475934 | 37.72 | capecleare |
In the waters around Cape Junken, there is strong evidence of a relationship between mean fish length and time over the years \(1994\) to \(2013\) (p-value\(<0.0001\) from t-stat\(=-5.370\) on \(18\) df).
The mean fish length in Cape Junken in \(2013\) is estimated to be \(6.8\) inches shorter than the mean fish length in Cape Junken in \(1994\), with a \(95\%\) confidence interval from \(4.35\) to \(9.29\) inches shorter.
Technically does not extend to all Seward boats/fish,
BUT....
No causal
There is moderate evidence that the log odds of fishing at Cape Cleare changes over time, assuming a linear trend over years \(1993\) to \(2014\) (p-value\(=0.02479\) from drop-in-deviance F-stat\(=5.89\)).
| YEAR coef | SE | F-stat | Pr(>F) | |
|---|---|---|---|---|
| capecleare | 0.0404 | 0.0161 | 5.891 | 0.0248 |
| resbay | -0.0463 | 0.0171 | 7.351 | 0.0134 |
| nuka | 0.0188 | 0.0385 | 0.238 | 0.6309 |
| patton | 0.0760 | 0.0200 | 12.532 | 0.0021 |
Each area modeled separately